The continued elucidation of gastric mucosal structure by recently developed techniques and the correlation of these findings to the secretory and metabolic functions of specific cells is the general objective of this research. Studies will include the parietal cell and surface mucous cell and, when appropriate, the chief, enterochromaffin, and mucous neck cells. Various approaches used in previous years will be extended and new applications of improved or new techniques will be undertaken. Studies on the gastric parietal cell will concentrate on the morphology of the cytoplasmic tubular system and its altered appearance after stimulation with such drugs as reserpine, pentagastrin, gastrin, insulin, micholyl, and other agents. Surface mucous cell structure and the morphological aspects of mucus biosynthesis will be studied. Agents that cause mucus secretion such as parasympathetic and sympathetic stimulation, and mucosal irritants will be used to follow experimental depletion and restoration of stored mucous granules. The usual ultrastructural techniques including autoradiographical localization of incorporated tracer molecules and histochemical techniques will be used. When appropriate, studies utilizing surface barrier breaking agents such as aspirin and ethanol will be continued. A long term objective that will be extended is the comparative study of vertebrate oxyntic or parietal cells.